Occupy Wall Street hit the 32-day mark Tuesday and has now gone global, tapping into a growing sense of worldwide economic anxiety. But can a largely leaderless, vaguely defined movement stand the test of time? How long can the protests continue?

Nobody knows for sure. But it's already reached a largely unexpected scale, according to observers.

"It's gone further than I would have guessed," said Michael Heaney, a University of Michigan political scientist who specializes in social movements and organization in U.S. politics. "It's amazing that it's lasted as long as it has. ... What we're seeing has no precedent."

Over the weekend, 19 more people were arrested in Washington, D.C., by Supreme Court police, while over 90 were taken into police custody in New York.

Multiple arrests were reported in Chicago, and about 150 people camped out by city hall in Minneapolis.

Just Watched

Inside Occupy Wall Street

Three key elements, according to Heaney, are now fueling the movement: continued economic discontent, growing media coverage, and a need to push back against harsh law enforcement tactics initially used against protesters.

"What's happened is that those three factors have enabled the movement to achieve critical mass, which has enabled the diffusion of this protest tactic," he told CNN.

Also worth noting: the role of the internet and social media in bringing would-be demonstrators together.

We're seeing the creation of "a much more decentralized, less expensive model (of social protest) that enables you to mobilize a much bigger group of people more quickly," he said.

At the start, Heaney said, many of the protesters were self-identified anarchists who had taken part in recent demonstrations held during high-profile meetings of the G-20, International Monetary Fund, and other international global economic institutions.

A number of the same people have also been protesting the U.S.-led wars in Iraq and Afghanistan, he noted.

People "have been trying to get this going for years," he said.

One question in the United States is whether Occupy Wall Street will eventually become a liberal counterweight to the conservative populism of the tea party movement. Heaney sees some similarity in terms of the sense of fear and anger driving both sides.

If the tea party was a conservative response to President Barack Obama's economic bailout plan in the spring of 2009, Occupy Wall Street came about partly due to liberals' reaction to the outcome of this summer's acrimonious debt-ceiling debate, Heaney argues. Obama and other top Democrats ultimately agreed to over $2 trillion in spending cuts without any tax hikes on Wall Street financiers or others considered responsible for the economic crisis.

Progressives "watched in horror" during the debt-ceiling debate, he said. "Obama showed that he wasn't able to deal" effectively with the right wing.

As a result, there's now an "acute sense of threat" on the political left that has encouraged certain people to take to the streets.

Until now, however, the tea party and Occupy Wall Street have differed sharply in terms of their emphasis on organization, with tea party activists far more willing to use traditional political strategies such as lobbying and fielding candidates for political office. Anarchist elements of the original Occupy Wall Street movement have neither the experience nor the inclination to do that, Heaney said.

Now, however, the movement has spread to labor unions and other organizations with more political experience and interest in building lasting political institutions. It is unclear to what extent -- if any -- those elements will ultimately co-opt the movement.

Economic angst is also fueling the protests overseas, though marchers in other countries have their set of specific grievances. Western Europe in particular is wrestling with the ramifications of a growing push for fiscal austerity, along with its own lingering anarchist movement.

The Europeans and others are "copying a protest," Heaney argued.

While the broader movement's future is hazy, it can already claim one key success: raising the salience of issues of economic inequality.

Liberal and conservative politicians are likely to start paying "a lot more attention to these issues than they otherwise would have," Heaney said.